Conclusion

The MOST forms a complex pattern of weak remote sidelobes which sweep the horizon during normal observations. The grid of 25 pointings used to measure the MOST's susceptibility to interference showed that in general the remote sidelobe gain of the telescope is 0.1, but these tests proved inadequate to specify the complete sidelobe pattern. In particular, they did not reveal the formation of out-of-focus grating lobes such as that found in the synthesis test. However, the collaborative test program has been broadly successful in determining the degree of protection required by the MOST to continue its high sensitivity Galactic and extragalactic radio observations.

The ITU has listed theshold levels of interference detrimental to radio astronomy continuum observations at internationally recognised frequencies for both single dish and interferometer modes of operation. Interpolating their values to 843MHz yields a threshold of -183dBWm. The MOST is generally some 10dB less sensitive to interference than the ITU threshold, except in the directions of grating lobes.

The ACA advisory guidelines, which are based on the analysis of the test data by the SMA, are adequate to protect the MOST.

© Copyright Astronomical Society of Australia 1997